GSM TRX Huawei: Time Slots vs. Channel Type relationship

Hi all,

I have a doubt: there is any standard or rule for Huawei GSM when it comes to define a new TRX regarding which channel type occupies each time slot.

For example, the BCCH has to occupy the time slot #0 of the first TRX.
Has the SDCCH and PDTCH channels have to occupy a preferred time slot within the TRX?

For different operators I've seen many differences and I want to know if there is any thumb rule (not neccesatily a mandatory rule, but a 'style' rule) for this assigment.

Thx.